Tracking eyes reveals surprises about autism

In studying autism, researchers have
struggled with a basic problem: interviewing subjects. Because the condition is
characterized by difficulty in social interactions, investigators have turned to
eye tracking. However, eye-tracking headgear is so obtrusive that it is tolerated
only by those with mild autism, making it nearly impossible to resolve some basic
questions.

Now, thanks to advances in cameras and some custom
engineering, researchers at the State University of New York at Binghamton’s
Institute for Child Development have overcome these issues and found some surprising
results: When given tasks, autistic children pay attention, are motivated and understand
what they are trying to do. “This process for our kids with autism is not
impaired,” said Raymond G. Romanczyk, director of the institute.

These preliminary and unpublished results,
which are to be presented at several conferences, don’t support current thinking.
Romanczyk and his group are planning further studies — experiments that have
long been contemplated, but that have been made possible only recently. “We’ve
wanted to do this research for about 15 years and, finally, the technology caught
up to what we needed,” he explained.

The setup at Binghamton consisted of
commercial and custom technology. The commercial component was an eye tracker from
Tobii Technology AB of Stockholm, Sweden. This stand-alone device doesn’t
require contact with the subject and can track the gaze at 50 fps with an accuracy
of about a half a degree. When located at a distance of 60 cm, the eye tracker can
follow the subject’s eyes even when the head moves over distances of tens
of centimeters. Besides following the subject’s gaze, it can measure pupil
size. It employs two near-infrared 875-nm LEDs for a source and collects the reflections
of that light off corneas. That information and other visual data are used in algorithms
that determine where each eye is looking and the overall gaze point.

Binghamton engineer Wayne Kashinsky,
who designed the setup, said that, about five years ago, higher-resolution cameras
using the FireWire standard came out from a variety of vendors. These allowed companies
such as Tobii Technology to work with a wider view of the face and to be farther
away. The devices, said Kashinsky, have a camera that images the entire face with
enough resolution to differentiate the pupils and to get the tracking information.

In the setup, the table was split into
two levels, with the eye tracker in plain sight between them. Because the eye tracker
worked only if the eyes were somewhere in a cube about 12.5 cm on a side, Kashinsky
mounted it on a motorized stand so that the angle could be changed. He combined
this with a motorized eight-way adjustable seat. The researchers could then bring
children who might not be all that cooperative into the right alignment and position.
What’s more, they could make minor adjustments to correct for some movement.

To gain further information, they also
used wireless and thin galvanic skin conductance measurement devices that Kashinsky
designed. Secured by a band in a child’s hand, the devices provided an indication
of the state of arousal — or anxiety — being experienced during the
study.

Using this equipment, the researchers
had groups of normal and autistic children of various ages perform tasks. Some were
imitations of simple play, such as picking up a toy airplane and making it fly.
These were done on the table and repeated with the objects near a model’s
face. Finally, the children were asked to imitate a model’s actions, such
as opening the mouth or blinking the eyes. A second part of the study replaced the
live model with a life-size image of the same person on a 42-in. plasma screen.

Synchronization played an important
role in gathering the data. The researchers used auditory instructions that only
the model could hear to initiate an action, simultaneously triggering the sensors.
This ensured that the eye tracker and galvanic skin conductors captured information
at the right moment.

Thanks to the eye movement and skin
conductance data, the researchers knew what the children were looking at and could
gauge their anxiety as they attempted various tasks. What they found, Romanczyk
said, was that the school of thought that autism is grounded in a lack of attention
didn’t appear to be correct. “As it turned out, the kids with autism
were not looking less at the face than the typical kids, but their performance was
much, much impaired,” he explained.
Researchers developed this setup to help with autism studies. It
consists of a split table and an eye tracker (the black box in the middle) mounted
to follow a subject’s eyes and, therefore, attention. A custom-designed galvanic
skin conductance device (seen here in the open hand) measures levels of anxiety
or arousal. Courtesy of Wayne Kashinsky, Raymond Romanczyk and the State University
of New York at Binghamton.
This performance difference between
normal and autistic subjects didn’t show up when subjects were imitating the
movement of a toy. However, it grew progressively greater the closer the task got
to the model’s face. But there wasn’t a spike in arousal or anxiety,
indicating that the difference was not because the autistic children were too nervous
to successfully complete the task. The problem, noted Romanczyk, appears to lie
in the processing of the information. The disconnect doesn’t seem to be attributable
to a lack of motivation or of not understanding the instructions.

Plans call for an extension of the
study from largely passive imitation to what is likely to be more demanding social
interaction. Romanczyk predicted that this phase will highlight differences between
autistic and normal children. “Our hunch is now we may in fact see a role
of arousal, a role of attention,” he said.

In studying social interactions, Kashinsky
contended that continued technological advances, particularly in computer processing
power, may help. Although cameras with five or more megapixels are available,
current computers aren’t powerful enough to convert the data that
these collect into eye-tracking information at 30 fps.

That computer limitation will change
over the next few years, and eye tracking systems could then have a field of view
several feet on a side. That would make it possible to image a group and tell where
each person was looking.